DE1607454A1 - Process for the production of finely divided metal powder - Google Patents

Description

Process for the production of finely divided metal powder

The invention relates to improved metal powders, particularly metal powders having a large surface area.

Fine metal powders are used to manufacture metal objects (by sintering the powder), as pigments, as fillers for plastics, as reagents, as rocket propellants, hard and soft solder, etc. are used.

It is known to use metal powder chemically, ζ.Β * by Condensation of the vapors or by precipitation from solution, but has been found to be mechanical Grinding is generally a cheaper method of making these powders. As pre-seals for grinding are suitable for example planetary ball mills, abrasion ball mills and vibratory ball mills.

It has also been known for some time that the grinding of metals in a grinding liquid, e.g. a petroleum fraction, Ethanol, methylene dichloride or n-heptane etc. Furthermore, the use of grinding aids, e.g. fatty acids and their metal salts, e.g. stearic acid and aluminum stearate. More details about this can be found in "Ultrafine Particles" by W.E. Kuhn, out-

909836/0740

given by Wiley 1963. It is stated that a grinding aid has the task of agglomerating the ground To prevent particles during milling.

However, the metal powders produced by known processes have the disadvantages of a small surface area and low lubricating effect.

The invention relates to finely divided metal powders which have a large surface area and high reactivity and are effective as a solid lubricant.

According to the invention, a finely divided powder is produced by grinding a metal in the presence of an organic semi-liquid and an organic additive which the Improved lubricity and extreme pressure properties and one or more of the elements sulfur, chlorine, phosphorus and contains nitrogen.

As organic grinding liquids are themselves liquids, distilling at 50O ⁰ C, a viscosity of less

ο surface tension as 600 cS at 37 | 8 C and a letter "** ^^"; of less than 72 dynes / cm at 25 ⁰ O, preferably from 10 to 40 dynes / cm at 25 ⁰ C. In a preferred embodiment of the invention, a hydrocarbon, in particular, for example, n-heptane, isooctane, cyclohexane, toluene, hexadecane or a hydrocarbon fraction obtained by distilling petroleum serves as the grinding liquid.

Organic additives that improve load bearing capacity are known and widely used in lubricants. Their task is to improve the wear-reducing properties and / or the extreme pressure properties of the lubricants. When two lubricated moving surfaces slide on each other under light load, they are separated by an elastic-hydrodynamic oil film. As the load increases, the thickness of the oil film decreases. If the oil film thickness reaches the dimensions of the surface, the film is penetrated by surface irregularities. · In this area, the effect is of comparable

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Wear-reducing additives that improve the strength of the oil film improve and thereby reduce the contact between the metals. If the load increases further, it falls the largest part of the oil film together, and the wear-preventing additives are no longer sufficient to protect the Surface. Extreme pressure additives are effective in this area by being inorganic with the metal surfaces Iron compounds react, which do not allow the metal surfaces sliding on one another to seize.

The expression "additives that increase the load-bearing capacity and pressure-absorbing capacity improve ", hereinafter referred to as" extreme pressure additives "for short, includes both anti-wear agents Additives as well as extreme pressure additives.

For the purposes of the invention, extreme pressure additives that contain one or more of the following elements are suitable: Chlorine, sulfur, phosphorus and nitrogen. Examples of suitable extreme pressure additives are organic chlorine-containing compounds, e.g. the low molecular weight chlorinated hydrocarbons, preferably those with 1-4 C atoms, e.g. carbon tetrachloride, Chlorobenzyl esters of alkylxanthic acids and thioacids, e.g. thiocarboxylic acid and chlorinated hydrocarbons

The covalent sulfur-containing compounds, e.g. diphenol polysulphides, are also suitable as high-pressure additives, for example di- (4-hydroxyphenol) polysulfide, alkyl and Aryl thioethers, alkyl and aryl thiocarbonates and thiocarbamates, sulfur-substituted carboxylic acid esters, e.g. Acetic acid ester, which are substituted by sulfur in the α-position, sulfurized polymers, e.g., sulfurized copolymers of 1,3-butadiene and styrene, the reaction product of sulfur and polyalkylene glycols, alkyl disulfides, e.g. di-n-butyl disulfide and di (2-ethylhexyl) disulfide, and biaryl disulfide, e.g., dibenzyl disulfide and di (aminobenzyl) disulfide.

More suitable. The high pressure additives are the phosphorus sulphurized ones organic compounds «Typical organic materials that can be phosphorus sulfurized are

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- 4 -

Oxygen-containing waxes, chlorinated phenols, wax-like Esters, cyclic ketones, hydrogenated spermacet oil, esters of unsaturated acids, e.g. glycol and glyceryl oleates, and abietic acid esters.

Other suitable extreme pressure additives are the organic ones Compounds containing phosphate or thiophosphate groups, e.g., triaromatic phosphates, e.g. Tricresyl phosphate, trialkyl phosphates, e.g. trifebutyl phosphate, and metal dialkyldithiophosphates, e.g., the zinc dialkyldithiophosphates. Metinorganic compounds, e.g. organotin dithiosphate and binaphthenate, can also be used as Hoohdruok additives.

Suitable nitrogenous compounds include phosphorus? midate, e.g. those described in British Patent 899.101, nitrobenzenes, nitronaphthalene,
Amiine phosphates, tetraalkylammonium phosphates and thiophosphates, and ehodanine and rhodanine derivatives.

All connections that support the load-bearing capacity and pressure-absorbing capacity of lubricants can be used for the purposes of the invention. If the org / anic Grinding liquid is also a high pressure additive, e.g. carbon tetrachloride, does not require any further high pressure additive to be added.

Any metals or alloys that can be milled are suitable for the purposes of the invention. Preferred metals are iron including mild steel and cast iron, and aluminum. Other suitable metals are the transition metals, e.g. nickel, cobalt, chromium and titanium, Copper and copper alloys such as brass.

In a preferred embodiment of the invention a high-speed rocker mill used. The grinding balls are preferably made of hardened steel * The grinding is preferably carried out until the metal powder formed has a surface area of at least

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2 m / g and preferably a bulk weight after shaking of less than 1 g / onr has «

It is assumed that the high pressure additives on the surface the metal particles are adsorbed and that in certain! "all a layer of chemically converted material the metal surface is formed during milling. For example, carbon tetrachloride can be used with the surface from particles of finely ground iron it exercises formation of Iron chlorides, etc. react.

Generally, the extreme pressure additive so effectively its extreme pressure properties in the formation of the fine-particle metal powder according to the invention, the better. However, high pressure additives can have different effectiveness when used with different metals, and it is useful to consider the metal to be ground when choosing the high pressure additive.

It has surprisingly been found that according to the Metal particles produced in the invention have good extreme pressure properties , d.lu lubricity and pressure absorption capacity. Because of these properties, the Powder for the production of reinforced, self-lubricating plastic stores, e.g. «. for nylon bearings made with iron o Suitable due to the nature of the metal surfaces the powders according to the invention are particularly useful as fillers, for plastics in general or as pigments, Eefcalysatoren etc..

It has also surprisingly been found that the finely divided Metal powder according to the invention can be used as a thickener for lubricating greases. For the production the finely divided metal can be of a lubricating grease simply stirred into a base oil, or any of them can be used Process used for the production of lubricating greases which are veryif t in the German patent.,. *., .. »« (Patent application B 89074 XV o / 23o) by the applicant are.

* ■ · Ό · ■ *

example

Iron powder was ground in a "Megapaet · Mark I" ball mill (manufacturer: Bilamec Limited) for 3 hours. In this mill, the grinding chambers consist of steel cylinders with an internal diameter of 38 mm and a length of 38 cm. They are almost filled with hardened steel balls of 6.35 mm 0th The mill is equipped with an electric motor of 1/8 HP and the vibration can be adjusted from 1-4 mm. In operation, each cylinder was completely filled with n-heptane in which a high pressure additive had been dissolved, after which the steel balls and 10-30 g of iron powder, the particles of which were added to a sieve with a size of TY-295 / ^ /. About 150-250 ml of n-heptane then remained in each cylinder. The ends were then closed with metal caps fitted with rubber seals, followed by grinding. After grinding, the balls were sieved from the slurry of iron powder and n-heptane and high pressure additive, and the treated iron powder was recovered by filtration, washing and drying.

The surface areas and bulk weights obtained using various additives are below given in Table I.

attempt High pressure at ζ ά Additional amount 1.0 1.0 I »luLver ge Ge in the powder of the ice « _Jhe bulk No· in n-heptane Dibenzy ^ ulfide in Grew .- # 2.0 2.0 found S, found Cl m2 / g ^erS) η of n-heptane phosphorus sulphurizing 0.5 0.5 Gew «- $ des in weight # des 2 ^m "shaking. 1 β plus Z us at as terpene " Powder ! Silvers ^: 5 g / _em 3 _# 2 Carbon tetrachloride - η η 0.5 - - 1.35 material 0.5 H-lauryl phosphorus _ 30th mm 3 -.amidat 7th 4th 1.0 Zinc dithiophosphate - 0.03 3 0.39 5 2.0 - - 2 0.40 tf-k 6th 0.5 0.66 - 3 - \ JLJ
O 7th 1.0 0.14 - 2 0.40 co
CX) 8th 2.0 0.07 2 - u>
cn ι 9 Di-tert-butyl disulfide 0.5 0.22 - 2 - f— \ 10 η η 0.13 - 2 0.52 CJ 11 u n 0.16 - 7th cn 12th 0.24 5 13th 0.5 - 7th 0.30 14th 0.16 - 0.34 3 «■ 15th -

* The bulk density was measured as follows: Part of the finely divided metal was in a measuring cylinder filled and shaken "until the measured tolumen was constant, whereupon the amount of powder was weighed.

The values in this table show that carbon tetrachloride has the largest surface area when grinding iron powder is achieved according to the invention. It can also be seen that with certain concentrations of the high pressure additives an optimal enlargement of the surface is obtained.

Nickel, molybdenum and chromium powders were also ground in n-heptane in the presence of carbon tetrachloride. The results are given in Table II below.

metal

High pressure additive in n-heptane

Additional amount in wt .- ^ of n-heptane plus additive

BET surface
of the powder
in m ² / g

Bulk weight after shaking in

1.ITi

2.Ni

3rd Ni μ 4th Mo « 5th Cr μ

6.ungemah- ^u lenes Ni

7. unmeshed Gr

Carbon tetrachloride

1 2

100 ** 1 1

2
4th
4th

0.34

0.44 0.34 3.5

3.87

** The grinding liquid consisted exclusively of carbon tetrachloride,

The carrying capacity of the powder was measured by making dispersions of the powder in a base oil in a four-ball machine have been checked. The results are given in Table III below.

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Table III

Base oil Pesticide wear and tear dispersed in the oil, Amount of pesticide in the oil, measured on

Weight -fo diameter of the polished surface, load 115 kg, 30 minutes

1. Medicines
sches
Paraffin oil "oleophilic" graphite * - 5 Plague eating in
less than
1 minute 2. dto. ¹¹ oleophilic "MoS ₂ ** 5 4.0 mm in 1 min. 3- dd Iron powder in
ground n-heptane,
no addition 10 0.99 mm in
50 minutes 4th dd Iron No. 2 10 Plague eating in
less than
1 minute 5. H Iron no. 11 10 1.08 mm in
30 minutes 6th t! 2.21 mm in
30 minutes

See German patent specification .......

(Patent application B 89 077 IVa / l2i)

See German patent specification

(Patent application B 89 075 IVa / l2n)

The values in this table show that the treated iron, the "oleophilic" molybdenum disulfide, the excellent "Maximum compressive strength" is equivalent in terms of load-bearing capacity and pressure absorption capacity.

The high pressure resistance of a manufactured according to the invention and iron powder dispersed in a BG 160/95 base oil was determined in a four-ball tester. This base oil has a Redwood I viscosity of 160 seconds at 60 ° C and a viscosity index of 95 · The results are below mentioned in Table IV.

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Table IV
Base oil 1. BG l6O / 95 2. BG l6o / 95

In the oil-dispersed solid - iron No. 2 Peststoffmenge in oil, wt -..%

Diameter of the ground surface

Load 15 kg, 60 minutes load 115 kg, 50 minutes Average Hertz load

O , 80 mm 0, 76 mm 2 , 64 mm 1, 5 mm 22nd , 6 .28, 7th

909836/0746

Claims (6)

Claims 1.) Process for the preparation of finely divided metal powder by grinding of a metal in an organic liquid, characterized in that 'it as the organic grinding liquid, those having a boiling point below 5OO ° C, a viscosity less than 600 cS at 38 ⁰ C and a surface tension of less than 72 dynes / cm at 25 ° C and containing one or more of the elements sulfur, phosphorus, chlorine and nitrogen containing a load-improving lubricant additive. "> 2.) The method according to claim 1, characterized in that there is used as the grinding liquid hydrocarbons. 3.) Method according to claim 1 or 2, characterized in that that low molecular weight chlorinated hydrocarbons, phosphorus sulphurized organic compounds, organic sulfur compounds, organic phosphates and thiophosphates or phosphoramidates are used . 4.) Method according to claim 1 to J, characterized in that that you can mix the metal in a vibrating ball mill up to grinds a surface of the metal powder of at least 2 m / g and a bulk density of less than 1 g / cnr. 5.) Method according to claim 1 to 4, characterized in that that the strength-improving additives in a weight corresponding to the metal or less Amount used, 6.) Use of the metal powder according to claim 1 to 5 as Plague lubricants. 909 # 36/0746